Sialic acids have been implicated in polysome binding. This research proposal deals with the investigation of the role of sialic acid metabolism in the regulation of the attachment of polysomes to the membranes of the endoplasmic reticulum. Chemical and enzymological studies will be conducted in rat organs (such as liver and mammary glands) undergoing physiological or experimentally induced changes in the relative proportions of free and membrane-bound polysomes. For the chemical studies, the membranes of the smooth and rough endoplasmic reticulum will be isolated and analyzed for total, lipid-bound and protein-bound sialic acids. In addition, changes in the distribution patterns of gangliosides and sialoglycoproteins present in these membranes will be investigated by thin-layer chromatography and by polyacrylamide gel electrophoresis respectively. For the enzymological studies, whole homogenates and subcellular fractions isolated from the same organs will be utilized to measure the levels of CMP-sialic acid synthetase, sialyl transferase and neuraminidase activities. Correlations between chemical and enzymological findings associated with changes in the relative proportions of free and membrane-bound polysomes will be examined in order to gain information on the cellular mechanism(s) involved in the binding and release of polysomes, a process which may play a fundamental role in the control of the biosynthesis of intra- and extracellular proteins. BIBLIOGRAPHIC REFERENCES: Membrane-Bound neuraminidases of Rat Liver. Neuraminidase Activity in Golgi Apparatus. G.S. Kishore, D.R.P. Tulsiani, V.P. Bhavanandan and R. Carubelli. J. Biol. chem. 250, 2655-2659 (1975). Neuraminidase Assay Utilizing Sialyl-Oligosaccharide Substrates with Tritium-Labeled Aglycone. V.P. Bhavanandan, A.K. Yeh, and R. Carubelli. Anal. Biochem. (in press).